Fixes golang/go#26078

Change-Id: Ie5a8c7028a755bc7a8d56abc4736a5f61ef91ce5
Reviewed-on: https://go-review.googlesource.com/121175
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>